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FreeBSDOperating system

CVE-2026-45257

HIGH · 7.8 CVSS v3.1 Published 2026-06-26
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The KTLS receive path decrypted each record in place, assuming that the mbufs holding received data were anonymous and safe to modify. This assumption does not hold for data placed on a socket by sendfile(2), which can reference file-backed memory directly through non-anonymous M_EXTPG pages or EXT_SFBUF mbufs. When the sender transmits such data over a loopback connection without enabling KTLS on the transmit side, the file-backed mbufs reach the receiver's decryption path unchanged. Decrypting a record in place then overwrites the backing file's page cache instead of a private copy of the data. An unprivileged local user who can read a file can overwrite its contents with data of their choosing by sending the file over a loopback connection on which they have enabled KTLS receive. The write modifies the page cache directly, so it bypasses file flags such as schg and is written back to disk. By overwriting a setuid binary or other trusted file, a local user can escalate privileges, potentially gaining full control of the affected system.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A race condition in the FreeBSD KTLS receive path allows decryption to modify file-backed mbufs in place, overwriting the source file's page cache. By sending a file via sendfile(2) over a loopback connection with KTLS receive enabled, an attacker can directly modify the file's content in the page cache, which then gets written back to disk, bypassing file permissions and immutable flags.

MitigationDisable or restrict KTLS receive functionality for unprivileged users, or apply the kernel patch that creates a private copy of mbuf data before decryption when file-backed mbufs are detected.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FreeBSDOperating system
Affected:= 14.3= 14.4= 15.0= 15.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check FreeBSD kernel version
    Run `uname -r` or `freebsd-version -k` to obtain the running kernel version
    Affected if The version matches 14.3, 14.4, 15.0, or 15.1
  2. Verify KTLS kernel module is loaded
    Run `kldstat | grep tls` or `kldstat` to list loaded kernel modules and look for ktls or tls related modules
    Affected if A KTLS-related kernel module (such as ktls or tls) is loaded into the kernel
  3. Confirm KTLS receive is enabled in the kernel
    Run `sysctl kern.ipc.tls.enable` or `sysctl kern.ipc.tls` to check if KTLS functionality is enabled
    Affected if The sysctl value indicates KTLS is enabled (typically set to 1)
  4. Detect active TLS connections using KTLS receive path
    Inspect network connections using KTLS by checking socket statistics via `netstat -anp | grep TLS` or examining process network usage with `systat -net`
    Affected if Active TLS connections are established that utilize the KTLS receive functionality

You are affected if your FreeBSD version is 14.3, 14.4, 15.0, or 15.1 AND the KTLS kernel module is loaded with receive functionality enabled, particularly when using sendfile(2) over TLS connections.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Disable or restrict KTLS receive functionality for unprivileged users, or apply the kernel patch that creates a private copy of mbuf data before decryption when file-backed mbufs are detected.

Recommended fix Moderate confidence

FreeBSD 14.4-STABLE or 15.2-STABLE (latest stable branch)

  1. Check FreeBSD security advisory for CVE-2026-45257 on security.freebsd.org
  2. Upgrade the FreeBSD kernel to the latest stable release or security patch
  3. Reboot the system to load the fixed kernel
  4. Verify the KTLS fix is applied by checking kernel version or running system with KTLS enabled
Caveat Kernel upgrade may require system reboot and could have compatibility implications with custom kernel modules

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in FreeBSD Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA6.0 h
30.0 hours of engineering $5,240
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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45257 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data